Phosphate-responsive 2D-metal–organic-framework-nanozymes for colorimetric detection of alkaline phosphatase

In this study, a simple colorimetric method with a tunable dynamic range for alkaline phosphatase (ALP) activity assay was developed by using a peroxidase-mimicking two-dimensional-metal-organic-framework (2D-MOF). Phosphates including pyrophosphate (PPi), ATP, and ADP inhibited the peroxidase-like activity of the 2D-MOF, while their hydrolytic product, phosphate (Pi), exhibited no such inhibitory ability. Therefore, by integrating with the ALP catalyzed hydrolytic reaction, a colorimetric method was developed for ALP activity quantification. Furthermore, by using different phosphates as inhibitors for the peroxidase-mimicking 2D-MOF, the dynamic range of this colorimetric method could be efficiently modulated. Three linear ranges of 2.5-20 U L^-1, 5-60 U L^-1, and 50-200 U L^-1 could be obtained by using PPi, ATP, and ADP as inhibitors, respectively. Other proteins exhibited negligible interference, demonstrating that the proposed sensing method possessed excellent selectivity for ALP. Moreover, the developed assay was applied to evaluate ALP inhibitors and construct logic gates. This work not only provides a promising method for ALP detection but also represents a major step towards nanozyme bioanalysis.